- Publishing House: The World of Music
- Author: Kim Un-bong, Kim Jung-yeon
- Sections: 96
- Size: 230*305mm
It is a collection of piano pieces arranged from OST of tvN's popular drama "It's Okay to Not Be Okay" to a piano score. There are Easy versions of Cherny 100~ and Original versions of Cherny 30 levels. Through QR codes, you can easily watch the author's piano lessons and videos of the entire song's performance that will help you practice playing.